Angiogenesis, the process of forming new capillary blood vessels from microvessels, occurs during embryonic development, wound healing and female menstruation, but not under normal conditions. A failure in angiogenesis regulatory system may lead to: angiogenesis-related diseases such as angioma, angiofibroma and blood vessel malformation; cardiovascular diseases such as arteriosclerosis, intravascular coagulation and edematous sclerosis; and ophthalmological diseases such as corneal transplantation-related neovasculogenesis, neovascular glaucoma, corneal disease, involutional macula, degeneration of macula, pterygium, retinal degeneration, retrolental fibroplasias and granular conjugativitis. In addition, such failure may result in chronic diseases such as rheumatism and dermatological diseases such as psoriasis, telangiectasis, pyogenic granuloma, seborrheic dermatitis and acne. Solid tumor growth and metastasis, in particular, are angiogenesis-dependent (Ophthalmol., 102, 1261-1262, 1995; J. Am. acad. Derm., 34(3), 486-497, 1996; Circulation, 93(4), 632-682, 1996; Cell, 86, 353-364, 1996).
Angiogenesis is accompanied by the processes of: degradation of the vascular basal membrane; migration and growth of the vascular endothelial cell; formation of canal cavity by differentiation of vascular endothelial cell; and reformation of the blood vessels. Normal angiogenesis occurs during the luteinization and placentation, but abnormal angiogenesis leads to such diseases as mentioned above. Therefore, there have been many attempts to develop compounds for the prevention and treatment of these angiogenesis-dependent diseases.
Arthritis, a well known inflammatory disease, is caused as an autoimmune disease. But if the abnormality continues to proceed, angiogenesis is induced by the chronic inflammation appearing in the synovial cavity in the joints and synovial cell. Then, the growth of vascular endothelial cell in the synovial cavity is induced by cytokine, which leads to the formation of articular lamina leak to eventually destroy such normal tissues as the cartilage which act as a cushion in the articulation (Koch A. E. et al., Arthritis Rheum., 29, 471-479, 1986; Stupack D. G., Braz. J. Med. Biol. Res., 32, 578-581, 1999; Koch A. E., Arthritis Rheum., 41, 951-962, 1998).
Angiogenesis is one of major causes of ophthalmological disease, millions of people over the word are suffering from the loss of their eye power (Jeffrey M. I. and Takayuki A., J. Clin. Invest., 103, 1231-1236, 1999). Such diseases as geriatric muscular degeneration, diabetic retinopathy, premature infant's retinopathy, neovascular glaucoma and corneal neovascularization are caused, at least partially, by angiogenesis (Adamin A. P., et al., Angiogenesis, 3, 9-14, 1999). Diabetic retinopathy, in particular, is a diabetic complication which leads to blindness through capillary vessel penetration into the vitrina.
The ocular tissue contains the least amount of blood vessels among all tissues, and abnormal blood vessel growth in the ocular tissue leads to blindness. Because there is no suitable treatment available for ophthalmological diseases caused by angiogenesis, only steroid or antibiotic treatment is practiced, together with cautery or photocoagulation at an advanced stage of the disease. However, these treatments are temporarily effective and the symptom recurs because of the failure to prevent angiogenesis. Therefore, an effective therapy for such diseases must be based on the inhibition of angiogenesis.
Psoriasis, represented especially by flush macula and scaly skin, is one of the proliferative disorders in the skin, and if not cured, it can cause pain and malformation. Normal horny cells usually divide once a month, but psoriatic skin cells, at least once a week. If the horny cell grows rapidly, angiogenesis takes place to supply blood (Folkman J., J. Invest. Dermatol., 59, 40-48, 1972).
Angiogenesis is critical to the growth and metastasis of cancer cell. If angiogenesis is inhibited and the supply of blood is prevented, cancer cells grow to a size of about 1-2 mm in diameter and remain localized (Folkman and Tyler, Cancer Invasion and Metastasis; Biologic Mechanisms and Therapy [S. B. Day ed.], Raven press, New York, p 94-103, 1997).
Hitherto, there have been reported such angiogenesis inhibitors as the fumagillin and its derivative called AGM-1470 which inhibit the vascular endothelial cell growth, platelet factor-4 and its synthetic peptide, herbimycin A and the collagenase inhibitory tetracycline antibiotics.
Although arginine deiminase has been reported to inhibit the growth of cancerous cells in vivo and in vitro (Takalcu et al., Int. J. Cancer, 51, 244-249, 1992; Komada et al., Int. J. Hematol., 65, 129-141, 1997; Misawa et al., J. Biotechnol., 36, 145-155, 1994; Miyazaki et al., Cancer Res., 50, 4522-4527, 1990; Sugimura et al., Melanoma Res., 2, 191-196, 1992), it has not yet been disclosed as an angiogenesis inhibitor.
The bioavailibility of a protein drug is generally low because it is easily hydrolyzed and degraded by enzymes in vivo after it is administered, and if an immune response is induced by repeated administration thereof, life-threatening hypersensitivity may develop; furthermore, its clearance is enhanced by the reticuloendothelial system (RES).
U.S. Pat. No. 4,179,337 discloses a peptide-polymer complex prepared by linking a peptide or polypeptide to a polyethylene glycol (hereinafter, PEG) having a molecular weight of 500-20,000 or a water-soluble polymer. The in vivo biological activity of this complex remains high while the immune response against the complex is suppressed.
Abuchowski et al. have shown that the in vivo half-lives of various PEG-conjugated proteins are prolonged and their immunogenicities were low in the plasma (Abuchowski et al., Cancer Biochem. Biophys., 7, 175-186, 1984), and Davis et al. have demonstrated that polyethylene glycol-uricase complex has an increased half-life and the side effect during the metabolism of uric acid is reduced (Davis et al., Lancet., 2, 281-283, 1981). These results suggest that biologically active peptides or proteins, when conjugated to PEG, exhibit prolonged half-lives, increased solubilities and reduced immune responses.
Arginine deiminase has been known as an anti-cancer agent, but not as an inhibitor of angiogenesis. The present inventors have identified for the first time that arginine deiminase has inhibitory activity against angiogenesis. Arginine deiminase obtained from microorganisms or prepared by a genetic recombination technique, or said arginine deiminase conjugated to polymers like PEG, may have an extended in vivo half-life, reduced immunogenicity, and high activity of angiogenesis inhibition. The present inventors have thus found that arginine deiminase may be advantageously used in a pharmaceutical composition for inhibiting angiogenesis.